Looks like “Captain America” — which opened to slightly better numbers than expected and captured No. 1 last week largely thanks to a huger-than-expected drop by “Harry Potter and the Deathly Hollows” — will be another one-week wonder in the top spot. Most prognosticators agree that “Cowboys and Aliens” will open in the mid-to-low ’40s — not historically huge numbers for a Steven Spielberg-produced sci-fi flick but better than his other, older-skewing period piece this summer, “Super 8.”

That will probably be good enough to get by the Captain, whose numbers for his period piece are expected to dip into the low ’30s without the repeat business that’s failed to materialize this season.The Universal-distributed “Cowboys and Aliens,” a fun genre mashup that gets three stars from yours truly in a review promoted on The Post’s front page today, is currently rating just 43 percent at Rotten Tomatoes — well behind the 80 for “Super 8,” which stars a bunch of unknowns as opposed to Daniel Craig and Harrison Ford.

There are two other newcomers in theaters today. Sony’s excerable “The Smurfs” — zero stars from me, 20 at RT — is expected to be in a neck-and-neck race for the No. 3 slot with Harry Potter, with both predicting to land in the $20M to $25M range.

The other debut is Warners’s well-reviewed “Crazy Stupid Love” (3 stars from Kyle, 74 at RT) which prognosticators believe will open in fifth place in the high teens — the same vicinity as last weekend’s slightly underperforming rom-com “Friends With Benefits,” which may indicate audiences are becoming sated with R-rated romantic comedies. “CSL” carries a PG-13.